[PATCH] Char: isicom, correct probing/removing

Don't forget to decrease card_count in fail paths and in remove function.
Also null board->base in such cases to point out, that this structure is
unused and thus can be reassigned.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>